The overall objective of this research is to test the efficacy of a new form of pediatric rehabilitation therapy -namely, Pediatric CI therapy - to promote new and improved motor behavior in young children with hemiparesis associated with cerebral palsy. This is based on a theoretically-grounded therapy shown to be effective with adult patients with chronic stroke and to produce cortical reorganization (cf. Taub et al., 1993; Liepert et al., 2000). Pediatric Cl therapy involves (1) total restraint of the unaffected upper extremity and (2) repetitive use of the affected extremity, using intensive shaping procedures for 6 hours/day for 21 consecutive days. The proposed research builds on findings from a preliminary study that demonstrated significant gains in young children's upper extremity skills following Pediatric Cl therapy. We propose to conduct a prospective, randomized controlled study with 52 children (ages 2-6) with hemiparetic cerebral palsy. The specific aims are:(1) to test the efficacy of Pediatric Cl therapy compared to Conventional therapy to improve upper extremity movement and functional use;(2) to evaluate whether improvement (if detected) is sustained over the next 12 months; and(3) to assess whether Pediatric Cl therapy is associated with significant gains in other adaptive behavior domains (e.g., trunk control, mobility, communication, and self-help skills).This research is of paramount significance because there currently are no forms of pediatric rehabilitation proven efficacious (Barry, 2001), despite widespread use of physical and occupational therapy in treatment of young children with cerebral palsy (Ramey et al; 2000).